Gas dishwasher control circuit



Sept. 22, 1964 J. w. CLAYWELL GAS DISHWASHER comm. CIRCUIT 2 Sheets-Sheet 1 Filed March 19, 1962 TIME CYCLE (WA/PT INVENTOR.

Sept. 22, 1964 J. w. CLAYWELL GAS DISHWASHER CONTROL CIRCUIT 2 Sheets-Sheet 2 Filed March 19, 1962 United States Patent 3,149,637 GAS BEHWASHER CGNTROL CHRCUIT Jack W. Ciaywell, Wisconsin Rapids, Wis, assignor to Preway Inc, a corporation of Wisconsin Filed Mar. 19, 1962, Ser. No. 18%,520 Claims. (ill. 154-57) This invention relates to a gas dishwasher and more particularly to a dishwasher which has improved results and operation due to the utilization of gas in heating or the water.

An object of this invention is to provide a new and improved gas dishwasher.

Another object of this invention is to provide a gas dishwasher in which gas is utilized to heat water within the washer whereby water can be used at a lower temperature and rapidly brought to the desired temperature due to the burning of gas with the cycle of the washer continuing once the water is at the desired temperature.

Another object of the invention is to provide a dishwasher as defined in the preceding paragraph in which the dishwasher has a sanitizing rinse cycle derived from the heating of the water to a sanitizing temperature in a relatively short period of time required for heating due to the use of gas and with the cycle of the dishwasher continuing after the elevated temperature is attained.

Another object of the invention is to provide a gas dishwasher as defined in the preceding paragraphs in which an electrical control circuit is provided including means for detecting both the desired wash and rinse temperatures of the water and causing the cycle of the dishwasher to continue after the temperatures are attained in ditierent parts of the cycle.

Still another object of the invention is to provide a gas dishwasher in which a gas valve supplies gas for heating the water and a pair of blowers are provided with a first blower supplying air for combustion and a second blower supplying air to the combustion products for dilution and cooling, thereof, with means detecting operation of both of said blowers before the gas valve is operated to commence flow of gas.

Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of the gas dishwasher with the door shown in open position and with the racks removed;

FiG. 2 is a wiring diagram of the circuit for the dishwasher; and

FIG. 3 is a time cycle chart showing the cycle of operation of the dishwasher and operation of the timer in achieving the cycle.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the invention with the understanding that the present disclosure is to be considered as an exempliiication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

The dishwasher is shown generally in PEG. 1 in which a cabinet It? has a front loading door 11 which is shown in open position for access to a tub 12 within the dishwasher. The dishwasher tub has a sump 13 in the bottom thereof through which a heat exchanger tube extends whereby gas supplied to a burner located in an end of the heat exchange tube causes heating of water within the sump for use in the washer. Water is caused to circulate within the tub by means of a circulation system including a circulating pump having an inlet connected to the sump and an outlet connected through suitable passages to a pair of spray arms mounted on the sides of the tub for rotation about a horizontal axis due to impelling force imparted by passage of water through nozzles carried on the spray arms. One of these spray arms is indicated at 15.

The foregoing sets forth the general nature of the dishwasher and reference may be had to the hereinafter mentioned copending applications of Jack W. Claywell for a more detailed disclosure of the dishwasher.

Referring to FIGS. 1 and 2 of the drawings, the water circulating system includes the sump 13 to which a circulating pump 20 is connected which through the aforesaid passages supplies water to the spray arms 15. This circulating system is disclosed in application Serial No. 28,895, filed May 13, 1960, and now Patent No. 3,104,- 669. This prior application also discloses the connection of a drain pump to the sump for discharging water from the dishwasher at the end of a cycle. The drain pump is disclosed herein at 21.

The heating means for the water embodies the heat exchange tube 14 located in the sump 13 which is heated by means of a gas burner at an end thereof which may be of the type disclosed in either my copending application Serial No. 90,332, filed February 20, 1961, now abandoned, or the application of I. W. Claywell and C. J. Pavlak, Serial No. 143,736, filed October 9, 1961.

Gas is supplied to the burner by means of a standard electrically operated gas valve 22 identified in FIG. 2 herein. Air for combustion is supplied to the burner by means of a combustion blower 23 which is also shown in the applications last referred to with the application Serial No. 90,332 showing a switch responsive to operation of the blower which is shown in FIG. 2 herein at 24.

The dishwasher cabinet has a foraminous grill 25 at the lower front thereof which permits air fiow therethrough and the products of combustion are exhausted through the grill after cooling and dilution by addition of air supplied thereto by means of a dilution blower 26 with the operation of this blower being detected by a pressure switch 27. The use of such blower for dilution and cooling of flue gases with exhaust to the front of the dishwasher is shown in my copending application Serial No. 143,737, filed October 9, 1961, now Patent No. 3,111,941.

Added components of the dishwasher are shown in the wiring diagram of FIG. 2 with a commercially available electrically operated water valve 3% provided for causing the .uOW of water into the dishwasher. A water level responsive switch 31 is provided to detect the presence of the right level of water in the sump 13. An ignition system for the dishwasher is indicated generally at A pair of thermostats for detecting a wash temperature of the water, a first rinse temperature and a second higher rinse temperature of the water at a succeeding point in the cycle are indicated at 33 and 34. A timer for controlling the cycle of the dishwasher is indicated generally at 35 and is shown at the right-hand side of the wiring diagram in PEG. 2. A commercially available rinse injector for introducing a wetting agent is indicated at 3-5 and a solenoid for opening the dishwasher door 11 near the end of the cycle is indicated at 37.

Interlock switches are provided and include a grill switch 33 for indicatit that the grill 25 is in place on the dishwasher front and a door switch 39 for indicating that the door is closed. Additionally a pilot light 40 is in the circuit to indicate that the washer is going through a cycle.

The timer 35 is a commercially available unit in which a timer motor 35:: drives a plurality of cams mounted on a common shaft with the cams being indicated at ift-45. Each of these cams controls the position of a central movable and downwardly biased arm having a switch contact indicated at 41a4-5a of a series of switches amass? having upper fixed contacts lllb45b and lower fixed contacts 41c45c. The cams 41-45 are provided with both high and low surfaces as well as intermediate surfaces whereby when one of the switch arms 4-la45a is on a cam high, the contact is made with the upper fixed contact of the corresponding switch, while if the movable switch arm is on a cam low a contact is made with the lower fixed contact and if the switch arm is on an intermediate level of the cam contact is not made with either the upper or the lower fixed contacts.

The central switch arms of the timer switches are connected to one side L2 of the line through the interlock grill switch 38 and a normally open switch 46 which is closed when the cycle of the dishwasher is started by a pull on a knob 47, with this switch being connected to line L2 by a line 48 and the other side of the switch being connected by a line 49 to the movable switch arm 41a. This switch arm is connected to the switch arm 43a through a line 50 and the switch arm 43a is connected through the door switch 39 which is closed when the dishwasher door 11 is closed to the switch arm 42a through lines 51 and 52. The switch arm 42a is connected to the switch arm 4451 through a line 53. This is the condition existing when the timer is initially operated and the pilot light 40 indicates the cycle has started by being lighted from the line 51 through a line 54 with the opposite side of the pilot light 49 being connected to the opposite side Ll of the line.

The circulating pump 2% is connected in a line 55 extending between the upper switch contact 4412 and the side L1 of the line. The drain pump 21 is connected by a line 56 extending between the lower fixed contact 44c and the side L1 or" the line. The water fill valve 30 is connected by a line 57 to the lower contact 42c and the side L1 of the line through the water level valve 31. The Water level valve 31 is shown in closed position in which a movable contact 58 engages a lower contact 59 to complete the circuit from lower contact 42c to the line L1. When the desired level of water is in the sump 13 of the dishwasher the movable contact 58 moves from engagement with the lower contact 59 to engagement with an upper contact 6% which is in a line 61. This results in breaking the circuit through the water valve 30 and connecting other components to the side Ll of the line through the line 61.

The rinse injector 36 is connected by a line 62 to the upper contact 4217 and by a line 63 to the side Ll of the line. The door solenoid 37 is connected by a line .64 to the lower contact 450 and by a line 65 and a line 66 to the side L1 of the line. The timer motor 35a is connected to the side Ll of the line through the line 66 and a line 67 and the other side or" the motor is connected through a line 68 to a junction point 69 with the movable switch arm 45a and a line 70 which connects into a line 71 in circuit with the lower contact 43c.

The pair of thermostats 33 and 34 are of generally the same construction with diiierent temperature responses, with the thermostat 33 having a heat responsive movable switch arm 72 which is normally in a closed position with a fixed contact 73 and when a predetermined temperature is reached, the arm '72 moves from engagement with fixed contact 73 into engagement with fixed contact 74. The fixed contact 74 is connected by a line '75 to the upper stationary contact 45]), while the fixed contact 73 is connected to a line 76. The thermostat 33 is the so-called low thermostat and is set to detect when the water in the sump 13 reaches the temperature for washing and a subsequent first rinse, which is approximately 150 F, or at least within a range of 140 F. to 160 F., since the lower minimum temperature should be sufi'icient to melt fats, while the upper temperature limit should not be exceeded since certain proteins, such as egg, start to set when exposed to a temperature in excess of 160 F.

The thermostat 34 is the high thermostat for detecting when the water has reached a sanitizing temperature of approximately 180 F. for the final rinse in the cycle of the washer. This thermostat has the bi-metal switch arm '77 normally in engagement with a fixed contact 73 and when the set temperature is reached, the arm moves into engagement with a fixed contact 79 and out of engagement with contact 78. The fixed contact 7? is connected by the line '71 to the lower contact 430, while the fixed contact 7 8 is connected to a line 80.

The movable switch arms 72 and 77 of thermostats 33 and 34, respectively, are connected to a thermostat common line 81 which is connected by a line 82 to the lower switch contact die. It will be noted that the line 8% also connects to the line 7d which is connected to the upper fixed contact 73 of the low thermostat 33 whereby the thermostats are in circuit with the combustion blower 23 and the dilution blower 26 through lines 83 and 84. The opposite sides or" the blowers are connected to the side Ll of the line through the water level switch 31, when the switch arm 58 is in its upper position, through a line 85.

The gas and ignition system, indicated generally at 32, embodies the gas valve 22 previously referred to which at one side is connected to the line 76 which has the pressure responsive switches 24 and 27 in series therewith whereby the gas valve 22 is not connected to the side L2 of the line through the timer until these switches 24 and 27 are closed. The other side of the gas valve is connected by a line 86 to the terminal 87 of a conducting leaf spring 38 which in normal inoperative position closes contacts $9 and has a normally opened contact 90. The normally closed contacts 89 connect to a line 91 having a resistor 92 of a fairly low value and a second resistor 93 of a rela tively high value in series with resistor 92 and a transformer primary coil 94 is also in series with the resistors, with the line 91 being connected through the aforesaid components to the side L1 of the line through line 61 and the water level switch. A secondary 95 of the trans former is grounded at one side and by a line 96 is connected to the spark electrode gas igniter 97, such as a spark plug, with the other side of the igniter being grounded. A flame detector switch has a movable contact 98 and in the start position connects a line 99 with a line 1% having a heating coil 161 connected at one side thereto and the other side of the coil connected by a line N92 to a junction between the resistors 92 and 93. When the movable contact 98 of the flame detector switch, which may be of bi-metal, senses the presence of a flame, the arm moves to an alternate position to engage a contact 133 and then connects the line 99 to a line 104 connected to the line 61 running to side Lll of the line through the water level switch which bypasses the transformer. The heating coil 101 is associated with a bi-metal element 105 carrying a contact we normally spaced from the contact 90 on the leaf spring 88 but which can be caused to make contact therewith as subsequently described.

The cycle of the dishwasher is shown in the time cycle chart of FIG. 3 with the cams 41-45 and the associated contacts and circuits being indicated. The time in which a certain circuit is completed is shown by the darkened sections of the intervals of the cycle with there being approximately eight degrees of angular rotation of the timer cams for each interval and in a preferred embodi ment each interval representing a time period of 45 seconds. Certain intervals are of indeterminate length, specifically intervals 4, 22, and 33, since at these times the gas system may be operating for heating of the water and when the temperature of the water is obtained, the cycle is again resumed.

From the chart it will be seen that at interval 1 cams 42, 43 and 44 have presented lows to their respective switch arms so as to engage the switch arms with the lower contacts 420, 43c and 440, with contact 420 connecting side L2 of the line with the water valve 30 and the water level switch 31, which is in the position shown in FIG. 2, whereby the valve is operated to obtain entry G of water into the dishwasher. The closing of contact 43c places the timer motor a in circuit through line 71 and line 68 and the closing of contact 440 places the drain pump 21 across lines L1, L2. This results in the timer operating and with the drain pump operating to take out the initial water from the washer since this water would normally be cool. At interval 2, the contact 44c has opened to discontinue operation of the drain pump while the timer and the water fill valve are still operating. The same conditions exist at interval 3 and it will be noted that the water level switch 31 will discontinue the operation when the desired amount of Water is received in the washer by the shifting of the movable contact arm 58 out of engagement with the contact 59. At this interval, the cam has closed the upper contact 455 so as to con nect the low thermostat contact 74 with the side L2 of the line. This is of no operative effect at this time.

At interval 4, the contact 43c has opened to stop the timer motor and the fill valve is closed it not already having been closed due to the water level switch 31. At this interval 4, contact 41c has closed to connect the thermostat common line 81 with the side L2 of the line. This through both the high and low thermostats places the line 88 in the circuit which places the blowers 23 and 26 in circuit with the blowers being connected to line L1 through the water level switch 31 since the contact 58 has now moved upwardly into engagement with fixed contact 60. If the water fill has not been adequate, the blowers will not operate and the cycle of the dishwasher will not continue. Once the blowers are operating, the switches 24 and 27 are closed to supply power to the gas valve 22 and the ignition circuit. This causes current to flow through the resistors 92, $3 and transformer primary 94 as well as the heater Till. The resistor $3 and heater 1% are in parallel and with the relative values most of the current flows through the heater 191. With current flowing, a high voltage is induced in the transformer secondary which creates the spark for igniting the gas. During this interval, the current in the heater heats the bi-metal strip 105, causing it to bend upwardly as shown slowly and gradually reducing the gap between the nor mally open contacts 90 and 1%. In normal operation before this gap can be materially reduced, however, the flame detector having the movable switch arm 93 operates to switch to a position to engage contact 103 to short circuit the transformer. This opens the circuit to the heater 101 and permits the bimetallic member 105 to cool and return to its original position. The switching of the flame detector switch also puts the high resistance resistor 93 in series with the resistor 92 and the gas valve to greatly reduce the current in the system; however, the current is suilicient to hold the gas valve 22 in its open position. The system is now in its normal running condition and will remain so until caused to change.

The condition is caused to change when the low thermostat 33 is satisfied, which causes the switch arm 72 to move into engagement with fixed contact 74, whereby voltage is supplied to timer motor 35a through the upper fixed contact 45b which is closed at interval 4 as shown in the chart. Initiation of operation of the timer motor moves the dishwasher into interval 5 which causes contact die to open to de-energize the thermostat common line 81 to discontinue operation of the blowers and cause the gas valve to close. Further at interval 5 the upper switch contact 4422 is closed to energize the circulating pump 26 in line and cause water to flow through the spray arms 15 for the wash cycle. This operation continues until interval 18 in which lower contact id-c is closed to energize the drain pump 21 to commence draining the wash water from the dishwasher and at interval 19 the drain pump continues to operate with the till valve 3% operated by closure of lower contact 420. The valve at this point is permitted to operate because the drain pump has operated to remove water from the dishwasher 6 to again move the switch arm 58 of the water level switch 31 into engagement with contact 59 in line 57.

Filling of the dishwasher continues as the timer corn tinues to operate and until the water level switch is again satisfied and shifted; however, at internal 21 contact 45b is closed. Nothing happens at this point because of this. At interval 22, the fill valve is closed if this has not al ready occurred due to the shifting of the water level switch 31 and contact 410 is closed to again energize the thermostat common line 81. The action at this point is the same as described in connection with intervals 4 and 5 with combustion taking place until the temperature of the water rises to a point to operate the low thermostat 33. When this occurs, the timer motor is again energized and interval 23 commences with the timer motor operating and the circulating pump 20 operating. This provides the first rinse operation. This rinse continues until in terval 2) at which time the drain pump 21 again operates due to closing of contact 44s, with this drain operation overlapping at interval 30 with further filling of the tub which continues through interval 32, unless previously interrupted by the water level switch 31. The drain pump has discontinued operation at the end of interval 3d.

At interval 33, contact 410 is closed to again energize the thermostat common 81; however, the distinction from the earlier similar operations is that contact 4512 has not closed, so that the contact is not placed in circuit with the contact '74 of the low thermostat 33. At interval 33 the blowers and ignition system are energized through the contact 78 of the high thermostat 34 because of the thermostat common line $1 being energized. The operation of heatin the water continues until the switch arm 77 of the high thermostat shifts into engagement with contact 79. This breaks the circuit to the blowers and the ignition system and the timer motor is again caused to operate by being connected to contact '79 through lines 7i) and 71 as Well as line 68. This shifts the cycle into interval 34 which initiates the high temperature sanitizing rinse operation and a wetting agent is injected by operation of the rinse injector valve 36 due to closing of the upper contact 4215. Also, the timer motor is operating and the circulating pump 2:? is operating.

At interval 36, the upper contact 41b is closed to bypass the switch which had been closed when the timer button 47 was pulled, to maintain the circuit energized even though the switch 46 opens. The switch 46 is caused to open by the timer automatically restoring the button 4'7 to its inner position awaiting a next cycle and the bypass through contact 41b places side L2 of the line in circuit with the central switch arm 41a. This causes the timer motor 35a to continue operating by power through line 5'6, contact 430, and lines 70 and 68. At interval 4%, the contact 44b has opened to discontinue operation of the circulating pump and the contact 440 has closed to start operation of the drain pump to evacuate water from the dishwasher with the evacuation continuing through interval 41 and at interval 42 the contact 450 closes to energize the door solenoid 37 to open the door 11 of the dishwasher, whereby drying of the dishes and utensils can take place during that and the last two intervals of the cycle which ends at interval 45.

In the event that water is sufiiciently hot to satisfy the thermostat as it enters the dishwasher, then the time interval required for heating the water would not take place and the cycle would move into the next interval.

1 claim:

1. In a gas dishwasher having a tub, means including an electrically operated gas valve for heating water in the tub, a blower for supplying combustion air to the heating means, a blower for supplying air to the combustion products for dilution and cooling thereof, means for detecting operation of said blowers, and a circuit includsaid detecting means and gas valve in series whereby the gas valve can not operate unless the blowers operate.

2. A control circuit for a gas dishwasher comprising, in combination, and having, in circuit: an electrically operated Water-fill valve for the dishwasher; a water circulating pump; a Water drain pump; a combustion air blower; a flue dilution air blower; an electrically operated gas valve; a gas burner ignition system; and a motor driven cam operated timer with switches for successively operating in a cycle the fill valve, the combustion and flue dilution air blowers and the gas valve and gas burner ignition system, the water circulating pump, and the water drain pump.

3. A control circuit as defined in claim 2 and including a door opening solenoid in the circuit which is actuated last in the cycle.

4. A control circuit as defined in claim 2 in which a switch is in series with the gas valve and closed by the operation of the combustion blower to require operation of the blower as a condition precedent to operation or" the gas valve.

5. A control circuit as defined in claim 9 in which a second switch is in series with gas valve and closed by operation of the flue dilution blower to require operation 8 of the latter blower as a condition precedent to operation of the gas valve.

References Cited in the file of this patent UNITED STATES PATENTS 1,323,216 Cornwall Nov. 25, 1919 1,559,727 Merseles Nov. 3, 1925 2,254,269 Clark et al Sept. 3, 1941 2,610,642 DAurora Sept. 16, 1952 2,619,097 Von Brornssen Nov. 25, 1952 2,671,037 Stoddard Mar. 2, 1954 2,677,368 Janecek May 4, 1954 2,722,225 Carson Nov. 1, 1955 2,771,894 Low Nov. 27, 1956 2,781,765 Steidley Feb. 19, 1957 2,841,136 Pettit et al. July 1, 1953 2,930,721 Tuthill Mar. 29, 1960 3,049,132 Gilson Aug. 14, 1962 3,049,133 Jacobs Aug. 14, 1962 3,064,662 Given et al Nov. 20, 1962 FOREIGN PATENTS 621,168 France Ian. 31, 1927 

1. IN A GAS DISHWASHER HAVING A TUB, MEANS INCLUDING AN ELECTRICALLY OPERATED GAS VALVE FOR HEATING WATER IN THE TUB, A BLOWER FOR SUPPLYING COMBUSTION AIR TO THE HEATING MEANS, A BLOWER FOR SUPPLYING AIR TO THE COMBUSTION PRODUCTS FOR DILUTION AND COOLING THEREOF, MEANS FOR DETECTING OPERATION OF SAID BLOWERS, AND A CIRCUIT INCLUDING SAID DETECTING MEANS AND GAS VALVE IN SERIES WHEREBY THE GAS VALVE CAN NOT OPERATE UNLESS THE BLOWERS OPERATE. 